Definitely not 2.7, since it's still on VS2008 and would require so many changes for this to matter that it's just not an issue; I'm not sure on 3.4. Is cabinet.lib available (and have everything we need) for MSVC10 and SDK 7.1 (which are the important targets for 3.4)?

AFAICT, cabinet.lib has been around since at least VS 2008, so 3.4 will be fine. But since it builds currently there's no point changing it. I'll just let my changes handle it for 3.5 and leave the older versions alone.